This is a proposal for the continuation of work in the development and clinical application of parallel processed high speed ultrasound phased array imaging systems. Over the past period extensive studies aimed at improving Exploso system performance have resulted in improved instrumentation. Based on the results it is proposed to extend the Explososcan approach to producing real time 3-D ultrasound images. New 2-D arrays and receive processing architectures are proposed which would permit 64 to 1 parallelism in the receive mode. Images will be displayed on standard 2-D displays and provisions made to permit the simultaneous display of several tomographic planes. Hardware and software will be developed to permit the display of projection images with perspective and real time C-mode images. Incorporation of custom VLSI circuits are contemplated to reduce system complexity and enhance performance. Explososcan methods will be incorporated in two real time flow imaging systems. The first is a high speed color Doppler unit now under construction which will have a frame rate 4 times higher than conventional units. The second uses speckle motion tracking rather than Doppler techniques and consequently is independent of errors introduced by the Doppler angle. The incorporation of flow imaging with multiplanar images to produce 3-D flow images is an additional goal. Another goal is t study motion of the left ventricle with high speed imaging to assess the possibility of detecting mechanical correlates of abnormal ventricular depolarization. All 3-D images and color Doppler results will be compared with standard clinical images and other Doppler results.